This invention relates to water-in-oil emulsion explosive compositions. In another aspect, this invention relates to improved water-in-oil emulsion explosive compositions that contain nitrates, perchlorates and occluded air, that are detonable by a standard No. 8 blasting cap, and that are made of non-explosive components. A further aspect of this invention relates to No. 8 cap sensitive water-in-oil emulsion explosives that contain no sensitizer other than occluded air.
Water-in-oil emulsion type blasting agents are disclosed by Bluhm in U.S. Pat. No 3,447,978. These emulsion type blasting agents contain an aqueous solution of inorganic oxidizer salt which is emulsified as the disperse phase within a continuous carbonaceous fuel phase, and a uniformly distributed gaseous component. Such emulsion type blasting agents have many advantages over water slurry type blasting agents, but they are not cap sensitive. Therefore, such materials require a booster in order to effect their detonation.
Cattermole et al, in U.S. Pat. No. Re. 28,060 teaches the addition of certain amine nitrate compounds to the water-in-oil emulsion compositions in order to assure that once detonated, the explosion will propagate in a 2 or 3 inch borehole. However, the mere addition of amine nitrates to the conventional water-in-oil emulsion type blasting agents will not render such materials cap senstive. U.S. Pat. No. 3,770,522 suggests that the addition of materials such as trinitrotoluene, pentaerythritol tetranitrate, and the like, to conventional water-in-oil blasting agents will render them cap sensitive. However, it is well known that such materials are high explosives and are more expensive than conventional ingredients that go into the water-in-oil emulsion blasting agents, and the resulting products do not adequately perform in small diameter boreholes and are undesirable from other standpoints.
U.S. Pat. Nos. 3,715,247 and 3,765,964 disclose that water-in-oil emulsion explosive compositions can be prepared which retain all the advantages of the emulsion blasting agents described above, but are cap sensitive without the use of an explosive ingredient. These latter two patents disclose the addition of a detonation sensitizer or catalyst, such as an inorganic metal compound of Atomic No. 13 or greater, and strontium compounds.
Therefore, water-in-oil emulsion explosive compositions are needed that achieve cap sensitivity without the use of sensitizers other than occluded air, yet are characterized by good low temperature detonability and extended storage life.